Math Accuracy Help

I have a bit of a math problem on my hand. I am putting together a little calculator for my home brewing adventures, to calculate potential in alcohol production. I got my formulas, and tested them in google sheets to make sure they were working. I translated them to a small VB program. Everything works… okay… with one minor problem.

If I say, have 1 + 1 ( this is a simplified version of the problem) and run it through my code, I end up with 2. On the excel sheet I also get 2. If I have 1 + 1.1, on the Excel sheet I get 2.1; in program it returns 1. If I have 1+ 1.5, in the excel sheet I get 2.5, in the program I get 2.5

I have everything set to as full a decimal place as possible. What would account for these wierd zones of refusal to update the results?